Hello Mojang Team,
I paste the command
/setblock ~ ~1 ~ wall_sign 2 replace {Text1:"[{text:\"[Kit]\",color:\"dark_gray\",bold:\"true\",clickEvent:{action:\"open_url\",value:\"scoreboard players set @p kit 1\"}}]",Text2:"[{text:\"Jumper\",color:\"gold\",italic:\"true\"}]"}
in a command block and activated it.
This command should place a sign at the coordinates ~ ~1 ~ facing North.
I used Version 15w35e
What actually happened was...:
My Client crashed but the Server was Okay.
When I joined, it crashed again.
I had to remove the Title Entity with MCedit to fix this bug.
Steps to Reproduce:
1. Place a command block on a wall facing South.
2. Paste the command above in the command block.
3. Activate it.
Linked issues
Comments

Does it still happen in 15w36c, if so foes it still happen if your update your letinent json to strict?
Letinent json is no longer supported
Strict is quotes around both json keys as json values, so